EVEREST IST - 2002 - 00185 : D23 : final report

Deliverable públic del projecte europeu EVERESTThis deliverable constitutes the final report of the project IST-2002-001858 EVEREST. After its successful completion, the project presents this document that firstly summarizes the context, goal and the approach objective of the project. Then it presents a concise summary of the major goals and results, as well as highlights the most valuable lessons derived form the project work. A list of deliverables and publications is included in the annex.Postprint (published version

Embedding Multi-Task Address-Event- Representation Computation

Address-Event-Representation, AER, is a communication protocol that is intended to transfer neuronal spikes between bioinspired chips. There are several AER tools to help to develop and test AER based systems, which may consist of a hierarchical structure with several chips that transmit spikes among them in real-time, while performing some processing. Although these tools reach very high bandwidth at the AER communication level, they require the use of a personal computer to allow the higher level processing of the event information. We propose the use of an embedded platform based on a multi-task operating system to allow both, the AER communication and processing without the requirement of either a laptop or a computer. In this paper, we present and study the performance of an embedded multi-task AER tool, connecting and programming it for processing Address-Event information from a spiking generator.Ministerio de Ciencia e Innovación TEC2006-11730-C03-0

Scalable Layer-2/Layer-3 Multistage Switching Architectures for Software Routers

Software routers are becoming an important alternative to proprietary and expensive network devices, because they exploit the economy of scale of the PC market and open-source software. When considering maximum performance in terms of throughput, PC-based routers suffer from limitations stemming from the single PC architecture, e.g., limited bus bandwidth, and high memory access latency. To overcome these limitations, in this paper we present a multistage architecture that combines a layer-2 load-balancer front-end and a layer-3 routing back-end, interconnected by standard Ethernet switches. Both the front-end and the back-end are implemented using standard PCs and open- source software. After describing the architecture, evaluation is performed on a lab test-bed, to show its scalability. While the proposed solution allows to increase performance of PC- based routers, it also allows to distribute packet manipulation functionalities, and to automatically recover from component failures

Anticipatory Buffer Control and Quality Selection for Wireless Video Streaming

Video streaming is in high demand by mobile users, as recent studies indicate. In cellular networks, however, the unreliable wireless channel leads to two major problems. Poor channel states degrade video quality and interrupt the playback when a user cannot sufficiently fill its local playout buffer: buffer underruns occur. In contrast to that, good channel conditions cause common greedy buffering schemes to pile up very long buffers. Such over-buffering wastes expensive wireless channel capacity. To keep buffering in balance, we employ a novel approach. Assuming that we can predict data rates, we plan the quality and download time of the video segments ahead. This anticipatory scheduling avoids buffer underruns by downloading a large number of segments before a channel outage occurs, without wasting wireless capacity by excessive buffering. We formalize this approach as an optimization problem and derive practical heuristics for segmented video streaming protocols (e.g., HLS or MPEG DASH). Simulation results and testbed measurements show that our solution essentially eliminates playback interruptions without significantly decreasing video quality

Techniques for publishing real-time data on a local area network

The primary objective of this thesis was to develop techniques for publishing real-time data on a Local Area Network (LAN) using the two transport protocols, Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). One of the main restrictions was that the Data Acquisition (DAQ) system, the server, which does time-critical functions, should not be interrupted as it sends the data to monitoring applications. It was also desired that the monitoring applications, the clients, receive most of the published data. The two protocols, TCP and UDP, were evaluated using programs developed in C/C++ and compiled with the Visual C 6.0 compiler under Windows 2000. An ordinary TCP server software, developed in C/C++, published 100,000 1400 Byte TCP segments on a 100 Megabit per second (Mbps) LAN. An ordinary TCP client software was coded in C/C++ which read the published data. After reading 30,000 segments, the client application paused for 5 sec and the effect of the delay on the server was analyzed. The procedure failed to satisfy the requirement not to interrupt the server because the server stopped publishing data during the delay period. A proposed solution put the server\u27s publishing procedure into a separate thread thereby isolating the server application as a whole from any client interference. The results proved this approach to be successful. It was also found that the server can maintain one-server-tomany-clients interaction if the bandwidth is reduced by the number of connected clients. Using UDP sockets, ordinary server and client applications were developed to evaluate the real-time performance of the standard UDP sockets as was done for the TCP sockets. The client recorded the percentage of datagrams successfully received. Though the client did not block the server, it did not always receive 100% of the published datagrams. The server, however, could use UDP broadcast and publish simultaneously to multiple clients without reducing bandwidth. To solve the delivery reliability problem, the approach implemented allowed the UDP client to detect and request a retransmission of datagrams that it loses. The improved UDP server had the ability to retransmit datagrams that are lost by its clients. It was determined that the server efficiently serviced retransmission requests from the clients for data rates up to 9MB/s. In cases where the client application was engaged in other activities beside reading data from the server, an ordinary UDP client read 100% of all published data only at rates below 4 MB/sec, while the improved client read 100% of data up to 6 MB/sec

Handover Mechanisms in ATM-based Mobile Systems

This paper presents two handover mechanisms that can be used in the access part of an ATM-based mobile system. The first handover mechanism, which is called ¿handover synchronised switching¿ is relatively simple and does not use any ATM multicasting or resynchronisation in the network. It assumes that there is sufficient time available such that all data and history information of the old path can be transferred to the mobile terminal (MT) before the actual handover to the new path takes place. It is possible that the time between a handover decision and the actual handover is too short to end the transmission on the old path gracefully (e.g., ending the interleaving matrix, ending transcoder functions, emptying intermediate buffers). A possible solution to this problem is given by the second handover mechanism, where multicast connections to all possible target radio systems (RAS) are used in the core network. This mechanism is called ¿handover with multicast support